oa The Latest Geological/Geophysical Interpretation of the NSW Murray Basin Basement

Under the NSW Government’s New Frontiers initiative, the Geological Survey of New South Wales has commenced an interpretation of regional geoscience datasets for the Ana Branch, Pooncarie, Booligal, Balranald, Hay and Deniliquin 1:250 000 scale map sheet areas. The aim is to encourage exploration in frontier areas of NSW by extrapolating the geology beneath covered areas using regional aeromagnetic, gravity, radiometric, Landsat7, seismic and borehole stratigraphy datasets.

The Pooncarie and Balranald 1:250 000 scale map sheet areas are the latest areas to be interpreted over the Murray Basin. They were predominantly interpreted using total magnetic intensity (TMI) data, first vertical derivative (1VD) TMI imagery, tilt-filtered TMI imagery, Bouguer gravity imagery, tilt-filtered Bouguer gravity imagery and Bouguer gravity multi-scale edge detection or “worms”.

Outcomes of this interpretation include: (1) pipe-like, magnetically susceptible sources that intrude the basement, interpreted as diatremes; (2) The Hay– Booligal Zone, which consists of Silurian–Devonian sediments overlying an interpreted basement of crystalline rocks; (3) A suture zone of S-type granites along the western border of the Hay-Booligal Zone. The eastern side is bounded by the Bootheragandra Fault; (4) Curvilinear magnetic trends, interpreted as the Stawell Zone in NSW, that wrap around the Hay–Booligal Zone, and represent turbidites deformed during the Delamerian Orogeny.

Results of this study provide minor adjustments to previously interpreted geological boundaries and that the sources, interpreted as diatremes, are not the origin of volcanic ash required for the formation of the Arumpo bentonite deposit.