Summary Of Data And Results Carnarvon Basin, Western Australia Exmouth Gulf Marine Seismic Survey Whaleback Seismic Survey Of West Australian Petroleum Pty Limited

A reconnaissance marine reflection seismic survey was conducted in 1961 by Seismograph Service Limited for West Australian Petroleum Pty Limited. The survey took place within the Carnarvon Basin in Western Australia, and covered Exmouth Gulf and the open coastal waters along the west coast of Western Australia from Frazer Island to Bernier Island (see Fig. 1). The project areas fall within Permit to Explore 28H.

The survey was a two-boat operation. In the Exmouth Gulf area the survey 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 purpose of the survey was to obtain additional information on the regional geology and to map the extension of known structures in the North-West Cape region of the Carnarvon Basin. Information was also sought on the nature of the pre-Cretaceous to post-Palaeozoic faulting. The survey commenced on 15th July, 1961, and terminated on 20th August, 1961; a total of 753 miles of traverse was shot.

The survey indicated that Exmouth Gulf is essentially synclinal in character in the Cretaceous and Tertiary sediments. Several major pre-Cretaceous fault trends which had already been mapped on land with the seismograph were followed beneath the Gulf. A pre-Cretaceous anticlinal axis underlies the Cape Range Anticline both to the north and to the south of the surface expression of the structure. An anticline was located trending north in the eastern part of the Gulf. A Cretaceous anticline near and parallel to the coast near Cardabia may be the extension of the Rough Range Anticline.

To the south of Point Maud, the survey provided a much-needed tie between the Rough Range-Cape Range area and the structurally complex area round the Salt Marsh. Some structural features were found in this southern area and the trend of major faults was established.

The geophysical operation undertaken in the Exmouth Gulf area, Western Australia, was subsidized under the Petroleum Search Subsidy Act 1959.

1961年，地震服务有限公司（Seismograph Service Limited）受西澳石油私人有限公司（West Australian Petroleum Pty Limited）委托，实施了一项海洋反射地震概查（reconnaissance marine reflection seismic survey）。本次勘探作业位于澳大利亚西部的卡那封盆地（Carnarvon Basin）范围内，覆盖埃克斯茅斯湾（Exmouth Gulf）以及澳大利亚西海岸弗雷泽岛（Frazer Island）至伯尼尔岛（Bernier Island）之间的近岸开阔海域（见图1），作业区域归属勘探许可28H号（Permit to Explore 28H）管辖。

本次勘探采用双船作业模式。在埃克斯茅斯湾区域，勘探采用Lorac无线电导航系统（Lorac radio navigational system）进行定位；西海岸段则通过六分仪测量岸标与地标夹角来确定测点位置。所有震源激发信号均记录于磁带上，后续处理为变面积记录剖面（variable-area record sections）。

本次勘探的目的是获取卡那封盆地西北角区域的区域地质补充资料，并编绘已知构造的延伸展布图；同时还旨在查明白垩纪前至古生代后断层的性质。勘探于1961年7月15日启动，同年8月20日结束，累计完成753英里的测线（traverse）采集。

勘探结果表明，埃克斯茅斯湾内的白垩系与第三系沉积物整体呈现向斜构造特征。此前已在陆地上通过地震勘探圈定的多条主要白垩纪前断层走向，在海湾下方得到延伸。开普岭背斜（Cape Range Anticline）的地表出露南北两侧下方，均存在白垩纪前背斜轴（anticlinal axis）。海湾东部还发现一条走向北的背斜构造。卡达比亚（Cardabia）附近沿海且与海岸平行的白垩系背斜，可能为拉夫岭背斜（Rough Range Anticline）的延伸构造。

在莫德角（Point Maud）以南区域，本次勘探填补了拉夫岭-开普岭区域与盐沼（Salt Marsh）周边复杂构造区之间的数据空白，新发现了该南部区域的若干构造特征，并明确了主要断层的走向。

本次在澳大利亚西部埃克斯茅斯湾开展的地球物理勘探作业，获得了《1959年石油勘探补贴法案》（Petroleum Search Subsidy Act 1959）的专项补贴。