New map shows weird magnetic anomaly lurking beneath Australia's Northern Territory

Magnetic map showing an anomaly in Australia's Northern Territory that is shaped like Australia.

Researchers have described a magnetic anomaly in Australia's Northern Territory that is shaped just like the country. (Image credit: CSIRO)

New mapping in Australia has revealed a strange dent in the magnetic field beneath the country's Northern Territory.

The Australia Magnetic Anomaly, named after its similarity in shape to the country, holds valuable information about Australia's geological history, including how different rock layers formed and acquired their distinctive magnetic properties.

A magnetic anomaly is a local variation in Earth's magnetic field caused by the magnetic properties of certain minerals and rocks, such as iron ore deposits, in the crust.

From the moment they form, rocks start to develop magnetic signatures that incorporate information about the direction of Earth's magnetic field at that specific time. This "magnetic memory," known as remanent magnetism, helps scientists reconstruct rocks' past.

However, the magnetic field occasionally flips, and tectonic processes can change rocks' orientation, which muddles the picture. But if scientists can decipher the various clues encrypted in a rock's magnetic signature, they can reconstruct exactly what the rock went through and when.

The Australia Magnetic Anomaly contains structures such as faults, folds and basins that traditional mapping techniques haven't been able to detect, according to the statement. To explore these hidden layers, Foss and his team used advanced modeling techniques to better visualize magnetic data collected during the Northern Territory Government's 1999 Bonney Well Survey.

For that survey, planes fitted with magnetometers — instruments that measure magnetic fields — flew across the Northern Territory in regular lines separated by about 1,300 feet (400 meters). Scientists previously tried to map these data, but the maps didn't always render magnetic signals clearly — particularly along the flight lines, according to the statement.

Map showing the location of the Australia Magnetic Anomaly in Australia. — The Australia Magnetic Anomaly, so called because it is shaped like the country, is located in the Northern Territory. (Image credit: CSIRO)

The new modeling has solved this problem. "My colleague, Dr Aaron Davis, created an innovative gridding algorithm which refined the dataset and produced cleaner, more consistent images," Foss said. "By improving how we process and model these datasets, we can extract more geological information than ever before."

The researchers identified subtle magnetic layers, as well as buried geological boundaries and structures that previous mapping didn't pick up.