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ABSTRACT: New approaches in analysis and interpretation of high resolution aeromagnetic fields in sedimentary basins

Irena Kivior , Archimedes Consulting, Adelaide Australia, [email protected]

The new approach in the analysis and interpretation of high-resolution magnetic data over the Cooper/Eromanga Basin, Beetaloo Sub-Basin, Bowen Basin, NW-Shelf, and others, allowed to detect sedimentological boundaries, delineate igneous bodies, and detect regional and local structures within the sediments and the underlying basement. These include fold structures, major faults zones and patterns of small fault-associated structures and often fracture patterns within different stratigraphic units.

To obtain a broad regional picture and an understanding of the distribution and character of magnetic anomalies arising from sediments and the underlying basement, gridded magnetic data was analysed using energy spectral analysis (ESA) and related filtering techniques and transformations.

To determine the position and depth of individual magnetic sources, magnetic anomalies were analysed using the automatic curve matching method (ACM) along profiles. Several hundred thousand magnetic anomalies were interpreted in each of the sedimentary basins. The ACM results were plotted as magnetic-source maps (MSM) for major stratigraphic units represented by crustal ‘depth-bands’.

The relationship of the MSM to the geology of each basin can be easily seen. It appears that the main trends of the magnetic lineaments, which persist at depth, reflect the characteristic structural grain of the analysed regions. The magnetic lineaments often represent fault zones and/or fault-associated structures. It has been confirmed that a large number of the defined magnetic lineaments correspond to the position of faults determined from seismic. A change in the azimuth-pattern of magnetic lineaments, could be an indication of the local stress field.

Major magnetic boundaries corresponding to stratigraphic unconformities have been detected and imaged in the Cooper/Eromanga Basin, Beetaloo Sub-basin and also on the NW-Shelf.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia