“Worming” in New South Wales

Summary

The regional geology of parts of the state of New South Wales is very poorly known because of a thick regolith cover that makes field mapping difficult. Geologists often rely on the interpretation of geophysical data to help with the regional mapping.

The use of potential field data in the interpretation of geological maps is very common. However, due to the non-uniqueness of potential field modelling, there can be no certain or unambiguous differentiation between different possible source rock geometries without reference to a priori information such as independent geological data. In order to overcome this problem, we use a wavelet analysis of potential field data, by looking at the horizontal gradient at different continuation levels. This method, also called multiscale edge detection (or worming), has proven to be a valuable additional tool for current regional mapping in NSW.

We have applied the edge detection method in several areas of NSW. In this paper, we present results from the Cobar Basin, and also the Koonenberry region in the north-west of NSW. In the Cobar area, the method has helped define the edges of the basin, the major faults as well as their dips, and the internal structure/architecture of the basin. In the Koonenberry region the worms were found to be related to major structures and intrusive margins, and were considered when defining the shape and dips of buried bodies in 2D modelling of cross sections. The method has added an additional degree of confidence in understanding the deep seated tectonic fabrics of these regions.

Key words::

• potential field data
• horizontal gradient
• worms
• Cobar
• Koonenberry