Blackall sits in sheep and cattle country in central western Queensland, and far beneath it lies the Adavale Basin, a stretch of ancient sea floor laid down between about 419 and 358 million years ago and hidden under younger basins. In October and November last year Geoscience Australia, working with the Geological Survey of Queensland, set up a rig about 63 kilometres south east of town and drilled the deepest hole in the agency's modern history. Borehole GA Enniskillen 1 reached 3,023 metres, roughly three times the height of the world's tallest building, and brought up 976 metres of solid rock core. One aim of the $30.9 million Data Driven Discoveries Program was to learn more about the Boree Salt, the only known thick layer of rock salt in eastern Australia, which could one day hold hydrogen in underground caverns. "We did not find any salt, but we did intercept other types of evaporative rocks," said Mitchell Bouma, head of the agency's Advice, Investment, Attraction and Analysis Branch. Those rocks form when a salty lake or a cut off arm of the sea dries out, and in his reading the halite "was dissolved from this location somewhere around 325 to 370 million years ago". What the core did hold was a reef: fossil corals, sea sponges, trilobites and ammonites, with ferns among them, fresh evidence of what the agency called a "relatively rich reef ecosystem" under the outback. Crispian Yeomans told the story for ABC Western Queensland.

Close up of grey fossil coral with a honeycomb pattern
Hexagonaria, a Devonian fossil coral, the honeycomb pattern of a reef builder of the same age. Photo: James St. John, CC BY 2.0.

Read the full story: Scientists to use Adavale Basin fossils to unlock secrets of giant fish, by Crispian Yeomans, ABC News.

Espen Knutsen, senior curator of palaeontology at the Queensland Museum, says little is known about the ancient reefs buried under Australia. A Geological Survey of Queensland report in 2007 described the fossil record of corals, molluscs and algae in the Bury Limestone as "rich, varied and largely undescribed", and most of what has been seen came up through mining or deep exploration. "Often we hear about things that are found at the surface," Dr Knutsen said. "Who knows what we might be able to find if we could really, really just sort of dig through and see what kind of fossils it preserved?" Geoffrey Gilleaudeau, a geologist at George Mason University in Virginia, flew to Australia in July to inspect the limestone. His question is about size. Devonian seas were home to some of the biggest fish of their age, and bigger animals need more oxygen, so he wants to know whether these rocks record a major rise in ocean oxygen like one already detected in North America. "We're trying to see if that's a global signal, and that's why we're looking at another place which is very, very far away in the Adavale Basin in Queensland," he said. Back near Blackall the borehole has been plugged and the site rehabilitated, and the data will be released once checked. Nearly a kilometre of sea floor from long before the dinosaurs now sits in core trays, waiting to be read. "We're excited to see what we can discover through improving our geological models," Mr Bouma said.

A dark fossil trilobite curled on pale stone
Phacops, a Devonian trilobite about one and a half centimetres across. Photo: James St. John, CC BY 2.0.

Our short take: the full story is by Crispian Yeomans for ABC News, ABC Western Queensland (30 September 2026), with the drilling facts from Geoscience Australia's own news page (10 December 2025) and program page.