L024 Wandagee Hill/Middalya seismic reflection survey, WA, 1955

Middalya in the Carnarvon Basin, Western Australia, during October 1955 by the Bureau of Mineral resources. The object of the survey was to assist in interpreting gravity results in the region. Prior to this survey the interpretation of the geology suggested that the deepest part of the Palaeozoic basin was in the Wandagee Hill area, but gravity results indicated that a basement ridge may exist in this same area.The seismic results indicate a sedimentary thickness of at least 17,000 ft between Wandagee Hill and Middalya and possibly 24,000 ft thickness to the east of Middalya. Although no useful information was obtained in the immediate vicinity of Wandagee Hill, extrapolation of results from farther east, suggests that the basement may be as shallow as 6000 ft just west of Wandagee Hill. This would confirm the interpretation of the gravity results at this location.The seismic cross-section shows that there may be a large elevation of the basement over a region about 20 miles west of Middalya between Shot-points 90 and 113. Although there is no direct evidence of this in the gravity results, it may be related to faulting, particularly a fault four miles east of Middalya that is indicated both by surface geology and by gravity results.

1955年10月，澳大利亚西部卡那封盆地（Carnarvon Basin）的米达利亚（Middalya）区域由澳大利亚矿产资源局（Bureau of Mineral Resources）实施了本次勘探。本次勘探的目的为辅助解读该区域的重力勘探成果（gravity results）。在本次勘探开展前，现有地质解译曾认为古生代盆地（Palaeozoic Basin）的最深沉积区位于旺达吉山（Wandagee Hill）一带，但重力勘探成果显示该区域可能存在一处基底隆起（basement ridge）。地震勘探成果表明，旺达吉山与米达利亚之间的沉积厚度至少达17000英尺（ft），米达利亚以东区域的沉积厚度可能达到24000英尺。尽管在旺达吉山的紧邻区域未获取到有效勘探数据，但通过东侧更远测点的成果外推可知，旺达吉山西侧不远处的基底埋深仅约6000英尺，该结论将佐证该点位的重力勘探解译结果。地震剖面显示，在米达利亚以西约20英里、炮点（Shot-point）90至113之间的区域，可能存在大范围的基底隆起。尽管重力勘探成果中未发现该构造的直接证据，但该构造可能与断层活动相关，尤其是米达利亚以东4英里处的一处断层——该断层同时被地表地质调查与重力勘探成果所证实。