Lost volcanoes among oil and gas

Researchers have uncovered around 100 previously undescribed ancient volcanoes buried deep beneath central Australia.

That’s both surprising and significant, they suggest.

Surprising because they have gone unnoticed despite half a century of oil and gas exploration and production in what are known as the Cooper-Eromanga Basins, and significant because it suggests a lot more volcanic activity in the Jurassic period than previously supposed.

Writing in the journal Gondwana Research, the team from Australia’s University of Adelaide and the University of Aberdeen, Scotland, describe using advanced subsurface imaging to identify a plethora of volcanic craters and lava flows, as well as the deeper magma chambers that fed them.

The volcanoes developed between 180 and 160 million years ago and have been subsequently buried beneath hundreds of meters of sedimentary – or layered – rocks.

“While the majority of Earth’s volcanic activity occurs at the boundaries of tectonic plates, or under the Earth’s oceans, this ancient Jurassic world developed deep within the interior of the Australian continent,” says University of Adelaide co-author Simon Holford.

“Its discovery raises the prospect that more undiscovered volcanic worlds reside beneath the poorly explored surface of Australia.”

The Cooper-Eromanga Basins, which cover the north-eastern corner of the state of South Australia and south-western corner of Queensland, is Australia’s largest onshore oil and gas producing region, and has been substantially explored.

“This has led to a massive amount of available data from underneath the ground but, despite this, the volcanics have never been properly understood in this region until now,” says Aberdeen’s Nick Schofield. 

“It changes how we understand processes that have operated in Earth’s past.”

The researchers have named their discovery the Warnie Volcanic Province after one of the drill holes that penetrated Jurassic volcanic rocks (Warnie East-1). It was named after former Australian cricketer Shane Warne. [Cricket explained here for those who require it.]

“We wrote much of the paper during a visit to Adelaide by the Aberdeen researchers, when a fair chunk was discussed and written at Adelaide Oval during an England vs Australia XI cricket match,” they acknowledge.